Abstract: A graphic user interface (GUI) modification method for changing the graphic user interface (GUI) of an application program, including the steps of storing property information of each component comprising the graphic user interface (GUI), and data for making a software program to display the graphic user interface (GUI) on a user monitor in real time by reading the property information of each component, separately, displaying corresponding property information among the stored property information to a display window, and updating property information by receiving a changed property value through the display window, and displaying changed graphic user interface (GUI), after receiving changed property information and operating the software program to display the graphic user interface (GUI). Therefore, a need to modify source code to change a property value can be eliminated because the property value can be changed easily.